With an eye on a promising commercial market, the mineral-rich provinces of western China – particularly Jinchang, Zunyi, Baiyin, and Shizuishan - with the help of foreign investors are pouring money into shape memory alloy (SMA) research and industrial development.
Shape memory alloys are now used in air conditioners, other home appliances, orthopedic implants, orthodontic wires as well as in the automobile industry. A fender-bender is no problem for the owner of a car that is made of shape memory alloy (SMA) – add a little heat and the dent will slide back into its original form.
The potential for engineering applications of shape memory alloys [originally detected in gold and cadmium] became possible in the early 1960s after a laboratory research team headed by William Beuhler at the U.S. Naval Ordnance Laboratory discovered the shape memory effect in an alloy of nickel and titanium. Named Nitinol (Nickel-Titanium Naval Ordnance Laboratory), this alloy was both less expensive and easier to work with than the original shape memory alloy.
Although many alloys can exhibit the shape memory effect, the ones of commercial interest must be able to withstand substantial amounts of strain as they change shape.
To date, the best alloys for commercial purposed have proved to be nickel-titanium alloys and copper-base alloys – and western China boasts the minerals that form these alloys in abundance.
One of the biggest commercial successes in the use of shape memory alloys in recent years has been in the field of medicine, thanks to their super elasticity. In orthodontics, wires made of shape memory alloys will gradually return to their original shape exerting a small and nearly constant force on misaligned teeth with much less patient discomfort than the steel variety.
Besides their use in orthodontics and orthopedic prostheses and implants, Ni-Ti elements are used in needles, catheters, and surgical instruments.
(china.org.cn by Shan Xingmei 06/28/2001)
